Selecting a subset of frequency resources based on measurements of candidate frequency resources

ABSTRACT

A method of scheduling transmissions to client devices comprises receiving feedback (f1a-f3d) about a plurality of candidate downlink frequency resources (91-94) from a plurality of client devices and/or measuring channel qualities of a plurality of candidate uplink frequency resources (95-98) from receptions of transmissions, e.g. of the feedback, by the plurality of client devices. The method further comprises selecting a subset (92) of the plurality of candidate downlink frequency resources and/or a subset (96) of the plurality of the candidate uplink frequency resources based on the received feedback and/or the measured channel qualities. The method further comprises scheduling transmissions (dd1-3) to the client devices on the selected subset of candidate downlink frequency resources and/or transmissions (ud1-3) from the client devices on the selected subset of uplink frequency resources.

RELATED APPLICATIONS

This application is the U.S. National Stage of International ApplicationNo. PCT/EP2018/069709, filed Jul. 20, 2018, which designates the U.S.,published in English, and claims priority under 35 U.S.C. § 119 or365(c) to European Application No. 17182498.0, filed Jul. 21, 2017. Theentire teachings of the above applications are incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to a system for scheduling transmissions to clientdevices and a client device for transmitting feedback to said system.

The invention further relates to a method of scheduling transmissions toclient devices and a method of transmitting feedback.

The invention also relates to a computer program product enabling acomputer system to perform such methods.

BACKGROUND OF THE INVENTION

Narrowband Internet of Things (NB-IoT) has been specified in 3GPPRelease 13 with the aim to efficiently support IoT applications inLTE-based mobile networks with the requirements of deep indoor coverage,low complexity, low cost devices and long device battery life, amongstothers.

There are two types of NB-IoT carriers specified in 3GPP Release 13,each occupying a bandwidth of 180 kHz, the same as one LTE PhysicalResource Block (i.e. 12 OFDM sub-carriers each with 15 kHz width):anchor carriers and non-anchor carriers. An anchor carrier carries allthe common control channels for NB-IoT (for the delivery of systeminformation, synchronization, etc.). There could be one or more anchorcarriers dedicated to NB-IoT applications. A non-anchor carrier does notcarry the common control channels of NB-IoT. In case the in-bandoperation mode of NB-IoT is used, the LTE Physical Resource Block (PRB)of the non-anchor carrier is not dedicated to NB-IoT, i.e. it can beshared by NB-IoT client devices (a client device is referred to as “UserEquipment” or “UE” in LTE) and regular (not NB-IoT capable) LTE clientdevices via PRB resource allocation done by e.g. a joint scheduler.

An idle NB-IoT client device camps on an anchor NB-IoT carrier and usesit for setting up the connection (i.e. paging and RACH procedure).During the connection set-up process (i.e. when transiting from RRC_Idleto RRC_Connected mode), the NB-IoT client device might be allocated ananchor or non-anchor NB-IoT carrier for its transmission/reception ofdata.

Typically, an LTE carrier is wideband and the radio propagationcondition is frequency-selective. At the exact locations of staticclient devices, the receive wideband signal may experience a “dip” atsome Physical Resource Blocks (assuming the in-band mode operation modeof NB-IoT is used), while it might experience much better radiocondition at some other PRBs. Typically, each static client deviceexperiences the frequency-selective channel differently: when for onestatic client device the PRB is in a “dip”, the same PRB might haverelatively very strong radio channel response for another static clientdevice. For mobile devices, the radio channel quality of particular PRBis varying over time due to its mobility and if a PRB may experience a“dip” this is temporary and changes as the devices move around in thecoverage area of the NB-IoT system.

In LTE, a scheduler assigns frequency and time resources as PRBs to aclient device as soon as there is data to transmit by or to the clientdevice. The smallest scheduling time interval is the transmission timeinterval (TTI). The most advanced resource assignment available in LTEis the so-called ‘channel aware’ time-frequency scheduling. For thedownlink, the scheduler learns the time-frequency fading per clientdevice via channel quality information (CQI) feedback from the clientdevice. Ideally, this feedback is per PRB. For the uplink, the schedulerresiding at the base station learns the time-frequency fading per clientdevice via so-called sounding reference signal (SRS) transmission perclient device. The SRS is a pilot signal transmitted over the wholefrequency band of the LTE carrier (e.g. a 10 MHz band) so the schedulercan measure the channel for that client device in each PRB. Based on thetime-frequency fading information determined for a client device, thescheduler assigns the PRBs that are ‘best’ for this client device tothis client device.

Although ‘channel aware’ time-frequency scheduling takes thetime-frequency fading per client device into account, which frequencyresources are used for anchor and non-anchor NB-IoT carriers isconfigured by operators manually. As a result, the frequency-selectiveradio channels are not taken into account sufficiently. This isespecially a problem for static client devices experiencing poor radioconditions (e.g. client devices installed at fixed locations deep in abuilding), as these client devices may experience unchanged radioconditions during the whole data transmission.

SUMMARY OF THE INVENTION

It is a first object of the invention to provide a system for schedulingtransmissions to client devices, which already takes into accountfrequency-selective radio channels before scheduling takes place.

It is a second object of the invention to provide a client device fortransmitting feedback to a system, which allows said system to alreadytake into account frequency-selective radio channels before schedulingtakes place.

It is a third object of the invention to provide a method of schedulingtransmissions to client devices, which already takes into accountfrequency-selective radio channels before scheduling takes place.

It is a fourth object of the invention to provide a method oftransmitting feedback to a system, which allows said system to alreadytake into account frequency-selective radio channels before schedulingtakes place.

According to the invention, the first object is realized in that thesystem comprises at least one receiver and at least one processorconfigured to use said at least one receiver to receive feedback about aplurality of candidate downlink frequency resources from a plurality ofclient devices and/or measure channel qualities of a plurality ofcandidate uplink frequency resources from receptions of transmissions bysaid plurality of client devices, select a subset of said plurality ofcandidate downlink frequency resources and/or a subset of said pluralityof candidate uplink frequency resources based on said received feedbackand/or said measured channel qualities, and schedule transmissions tosaid plurality of client devices on said selected subset of candidatedownlink frequency resources and/or transmissions from said plurality ofclient devices on said selected subset of uplink frequency resources.

By selecting a subset of frequency resources from candidate frequencyresources based on measurements by a plurality of client devices and/orby measuring transmissions of a plurality of client devices, frequencyresources may be automatically instead of manually selected while takinginto account frequency-selective radio channels in this selection step,so before scheduling takes place. Thus, the real deployment environmentof client devices is taken into account and better overall performanceis achieved. Moreover, an optimized frequency resource selection maylead to increased spectral efficiency and reduced power consumption bythe client devices.

A frequency resource may be a frequency band, for example. The candidatedownlink frequency resources may comprise contiguous and/ornon-contiguous frequency bands. The candidate uplink frequency resourcesmay comprise contiguous and/or non-contiguous frequency bands. Saidsystem may further comprise at least one transmitter and said at leastone processor may be configured to use said at least one transmitter totransmit wireless signals on said plurality of candidate downlinkfrequency resources.

Said plurality of client devices may comprise one or more idle clientdevices. By not only selecting a subset of frequency resources fromcandidate frequency resources based on measurements by active clientdevices and/or by measuring transmissions of active client devices, butalso based on measurements by idle client devices and/or by measuringtransmissions of idle client devices (e.g. when triggered to report onsignal quality of candidate frequency resources), the selection may takeinto account more client devices. This is especially beneficial when theidle client devices are static and are thus going to be in the samelocation when they are active as when they are idle.

Said at least one processor may be configured to use said at least onereceiver to receive said feedback about said plurality of candidatedownlink frequency resources on said plurality of candidate uplinkfrequency resources and measure said channel quality of said pluralityof candidate uplink frequency resources from receptions of said feedbackon said plurality of candidate uplink frequency resources. This makes itunnecessary for the client devices to transmit pilot signals like thesounding reference signals transmitted when using ‘channel aware’time-frequency scheduling in uplink, and thereby reduces overhead.

At least one of said plurality of candidate downlink frequency resourcesmay be paired with at least one of said plurality of candidate uplinkfrequency resources and said at least one processor may be configured touse said at least one receiver to receive said feedback about said atleast one candidate downlink frequency resource on the at least onecandidate uplink frequency resource paired with said at least onecandidate downlink frequency resource. Thus, in case a pair of uplinkand downlink frequency resources, i.e. an uplink frequency resource witha pre-defined relative frequency offset compared to a downlink frequencyresource, is used and the system receives feedback on the uplinkfrequency resource, the system knows that the feedback relates to thepaired downlink frequency resource.

Said feedback may comprise an identification of one or more candidatedownlink frequency resources to which said feedback relates. In case anuplink frequency resource has not been paired with a downlink frequencyresource, this identification allows the system to identify to whichdownlink frequency resource feedback from a client device on this uplinkfrequency resource relates. Thus, the assigned downlink and uplinkfrequency resources do not necessarily need to be paired.

At least one of said plurality of candidate downlink frequency resourcesmay be paired with at least one of said plurality of candidate uplinkfrequency resources and said at least one processor may be configured todetermine at least one combined quality for at least one pair ofcandidate downlink and uplink frequency resources and select a subset ofsaid plurality of candidate downlink frequency resources and a subset ofsaid plurality of candidate uplink frequency resources based on said atleast one combined quality. If the assigned downlink and uplinkfrequency resources need to be paired, then the selection shouldpreferably consider the uplink and downlink jointly, i.e. determine anduse a combined/joint quality measure for a paired downlink frequencyresource and uplink frequency resource.

Said at least one processor may be further configured to scheduletransmissions to a mobile client device on said selected subset ofcandidate downlink frequency resources and/or transmissions from saidmobile client device on said selected subset of uplink frequencyresources, said selected subset of candidate downlink frequencyresources not being based on feedback received from said mobile clientdevice and/or said selected subset of candidate uplink frequencyresources not being based on a channel quality measured from a receptionof a transmission by said mobile device. As mobile client devicesnormally experience changing radio conditions during the whole datatransmission, statically configured/selected frequency resources areless of a problem for mobile client devices. This is because a ‘dip’ inthe quality of the radio conditions for a particular frequency resourceis of temporary nature due to the device mobility. It is therefore notnecessary to select a subset of downlink frequency resources based onfeedback received from a mobile client device and/or select a subset ofuplink frequency resources based on a channel quality measured based ona reception of a transmission by a mobile device.

Said wireless signals transmitted by said at least one processor usingsaid at least one transmitter on said plurality of candidate downlinkfrequency resources may be pilot signals. Said pilot signals may benarrowband reference signals or cell specific reference signals, forexample. Measurements on pilot signals are well known and therefore easyto implement.

Said at least one processor may be configured to use said at least onetransmitter to inform said plurality of client devices of at least onetime at which it will start transmitting said wireless signals on saidplurality of candidate downlink frequency resources. Since transmittingthe wireless signals on many candidate downlink frequency resourceswould use a significant amount of resources, it would not be efficientto transmit the wireless signals continuously. Instead, the wirelesssignals may be transmitted at certain times. These times, e.g. the firstminute of every hour or every second hour, may be communicated to theclient devices or, alternatively, configured in advance.

According to the invention, the second object is realized in that theclient device comprises at least one receiver, at least one transmitter,and at least one processor configured to use said at least one receiverto measure at least one channel quality of at least one candidatedownlink frequency resource from at least one reception of at least onetransmission by a transmitting system on said at least one candidatedownlink frequency resource, and use said at least one transmitter totransmit feedback based on one or more of said at least one measuredchannel quality to said transmitting system on a plurality of candidateuplink frequency resources. As this allows the system to measure thechannel qualities of the candidate uplink frequency resources based onreceptions of the feedback, it is unnecessary for the client device totransmit pilot signals like the sounding reference signals transmittedwhen using ‘channel aware’ time-frequency scheduling in uplink, andthereby reduces overhead.

According to the invention, the third object is realized in that themethod of assigning frequency resources to a plurality of client devicescomprises receiving feedback about a plurality of candidate downlinkfrequency resources from a plurality of client devices and/or measuringchannel qualities of a plurality of candidate uplink frequency resourcesfrom receptions of transmissions by said plurality of client devices,selecting a subset of said plurality of candidate downlink frequencyresources and/or a subset of said plurality of said candidate uplinkfrequency resources based on said received feedback and/or said measuredchannel qualities, and scheduling transmissions to said plurality ofclient devices on said selected subset of candidate downlink frequencyresources and/or transmissions from said plurality of client devices onsaid selected subset of uplink frequency resources. Said method may beperformed by software running on a programmable device. This softwaremay be provided as a computer program product.

According to the invention, the fourth object is realized in that themethod of transmitting feedback comprises measuring at least one channelquality of at least one candidate downlink frequency resource from atleast one reception of at least one transmission by a transmittingsystem on said at least one candidate downlink frequency resource andtransmitting feedback based on one or more of said at least one measuredchannel quality to said transmitting system on a plurality of candidateuplink frequency resources. Said method may be performed by softwarerunning on a programmable device. This software may be provided as acomputer program product.

Said method may be performed by software running on a programmabledevice. This software may be provided as a computer program product.

Moreover, a computer program for carrying out the methods describedherein, as well as a non-transitory computer readable storage-mediumstoring the computer program are provided. A computer program may, forexample, be downloaded by or uploaded to an existing device or be storedupon manufacturing of these systems.

A non-transitory computer-readable storage medium stores at least afirst software code portion, the first software code portion, whenexecuted or processed by a computer, being configured to performexecutable operations comprising: receiving feedback about a pluralityof candidate downlink frequency resources from a plurality of clientdevices and/or measuring channel qualities of a plurality of candidateuplink frequency resources from receptions of transmissions by saidplurality of client devices selecting a subset of said plurality ofcandidate downlink frequency resources and/or a subset of said pluralityof said candidate uplink frequency resources based on said receivedfeedback and/or said measured channel qualities, and schedulingtransmissions to said plurality of client devices on said selectedsubset of candidate downlink frequency resources and/or transmissionsfrom said plurality of client devices on said selected subset of uplinkfrequency resources.

A non-transitory computer-readable storage medium stores at least asecond software code portion, the second software code portion, whenexecuted or processed by a computer, being configured to performexecutable operations comprising: measuring at least one channel qualityof at least one candidate downlink frequency resource from at least onereception of at least one transmission by a transmitting system on saidat least one candidate downlink frequency resource and transmittingfeedback based on one or more of said at least one measured channelquality to said transmitting system on a plurality of candidate uplinkfrequency resources.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a device, a method or a computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit”, “module” or “system.”Functions described in this disclosure may be implemented as analgorithm executed by a processor/microprocessor of a computer.Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied, e.g., stored,thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples of a computer readable storage medium may include, butare not limited to, the following: an electrical connection having oneor more wires, a portable computer diskette, a hard disk, a randomaccess memory (RAM), a read-only memory (ROM), an erasable programmableread-only memory (EPROM or Flash memory), an optical fiber, a portablecompact disc read-only memory (CD-ROM), an optical storage device, amagnetic storage device, or any suitable combination of the foregoing.In the context of the present invention, a computer readable storagemedium may be any tangible medium that can contain, or store, a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber, cable, RF, etc., or any suitable combination ofthe foregoing. Computer program code for carrying out operations foraspects of the present invention may be written in any combination ofone or more programming languages, including an object orientedprogramming language such as Java™, Smalltalk, C++ or the like andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The program codemay execute entirely on the user's computer, partly on the user'scomputer, as a stand-alone software package, partly on the user'scomputer and partly on a remote computer, or entirely on the remotecomputer or server. In the latter scenario, the remote computer may beconnected to the user's computer through any type of network, includinga local area network (LAN) or a wide area network (WAN), or theconnection may be made to an external computer (for example, through theInternet using an Internet Service Provider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of thepresent invention. It will be understood that each block of theflowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor, in particular amicroprocessor or a central processing unit (CPU), of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer, other programmable dataprocessing apparatus, or other devices create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof devices, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblocks may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustrations,and combinations of blocks in the block diagrams and/or flowchartillustrations, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention are apparent from and will befurther elucidated, by way of example, with reference to the drawings,in which:

FIG. 1 depicts an environment comprising embodiments of a system andclient devices of the invention;

FIG. 2 is a block diagram of the system and one of the client devices ofFIG. 1;

FIG. 3 is a flow diagram of a first embodiment of the methods of theinvention;

FIG. 4 is a flow diagram of a second embodiment of the methods of theinvention;

FIG. 5 shows a first example of a resource allocation in relation toFIG. 3;

FIG. 6 shows a second example of a resource allocation in relation toFIG. 4;

FIG. 7 is a flow diagram of a third embodiment of the methods of theinvention;

FIG. 8 is a flow diagram of a fourth embodiment of the methods of theinvention;

FIG. 9 shows a third example of a resource allocation in relation toFIG. 7;

FIG. 10 shows a fourth example of a resource allocation in relation toFIG. 8;

FIG. 11 shows a fifth example of a resource allocation in relation toFIG. 8;

FIG. 12 shows a sixth example of a resource allocation in relation toFIG. 8;

FIG. 13 is a block diagram of an exemplary cellular telecommunicationsystem used in an embodiment of the device and the system of theinvention; and

FIG. 14 is a block diagram of an exemplary data processing system forperforming the methods of the invention.

Corresponding elements in the drawings are denoted by the same referencenumeral.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an environment comprising an embodiment of the system forscheduling transmissions to client devices, base station 1 (e.g. an LTEeNodeB), and embodiments of the client devices for transmittingfeedback, static client devices 11-15. In FIG. 1, the static clientdevices 11-15 are located in a building 21 and mobile client devices16-19 are vehicles driving on a road.

The base station 1 comprises a transceiver 3 and a processor 5, see FIG.2. The processor 5 is configured to use the transceiver 3 to receivefeedback about a plurality of candidate downlink frequency resourcesfrom the plurality of static client devices 11-15 and/or measure channelqualities of a plurality of candidate uplink frequency resources fromreceptions of transmissions by the plurality of static client devices11-15. The plurality of static client devices 11-15 comprises one ormore active client devices and one or more idle client devices. Theprocessor 5 is further configured to select a subset of the plurality ofcandidate downlink frequency resources and/or a subset of the pluralityof candidate uplink frequency resources based on the received feedbackand/or the measured channel qualities. The processor 5 is furtherconfigured to schedule transmissions to the plurality of client deviceson the selected subset of candidate downlink frequency resources and/ortransmissions from the plurality of static client devices 11-15 on theselected subset of uplink frequency resources. In the embodiment of FIG.2, the base station 1 further comprises storage means 7, e.g. forstoring the selection/configuration and/or the schedule.

The selected uplink frequency resource(s) and the selected downlinkfrequency resource(s) may be used as NB-IoT anchor carriers, forexample. The selected uplink frequency resource(s) and the selecteddownlink frequency resource(s) may optionally be used as NB-IoTnon-anchor carriers. Alternatively, the above-mentioned measurementsand/or feedback may be re-used or measurements may be performed andfeedback may be transmitted in the same manner to determine on whichnon-anchor carrier(s) to schedule transmissions.

The static client device 11 comprises a transceiver 33 and a processor35, see FIG. 2. The processor 35 is configured to use the transceiver 33to measure at least one channel quality of at least one candidatedownlink frequency resource from at least one reception of at least onetransmission by the base station 1 on the at least one candidatedownlink frequency resource. The processor 35 is further configured touse the transceiver 33 to transmit feedback based on one or more of theat least one measured channel quality to the base station 1 on aplurality of candidate uplink frequency resources. The static clientdevices 12-15 comprise a transceiver and a processor configured asdescribed above. In the embodiment of FIG. 2, the static client device11 further comprises a sensor 39. The static client devices 12-15comprise a similar sensor. These sensors may be smart electricitysensors, for example.

In the embodiment of FIG. 2, the processor 5 is configured to use thetransceiver 3 to receive the feedback about the plurality of candidatedownlink frequency resources on the plurality of candidate uplinkfrequency resources and measure the channel quality of the plurality ofcandidate uplink frequency resources from receptions of the feedback onthe plurality of candidate uplink frequency resources.

In the embodiment of FIG. 2, the processor 5 is configured to use thereceiver 3 to receive the feedback about at least one candidate downlinkfrequency resource on the at least one candidate uplink frequencyresource paired with the at least one candidate downlink frequencyresource, if such a pairing has been specified. The feedback comprisesan identification of one or more candidate downlink frequency resourcesto which the feedback relates when the feedback is transmitted on anunpaired candidate uplink frequency resource.

The processor 5 is further configured to determine at least one combinedquality for at least one pair of candidate downlink and uplink frequencyresources and select a subset of the plurality of candidate downlinkfrequency resources and a subset of the plurality of candidate uplinkfrequency resources based on the at least one combined quality if such apairing has been specified. Separate (e.g. channel) qualities may beused for non-paired candidate downlink and uplink frequency resources.In practice, most likely either all candidate downlink and uplinkfrequency resources are paired or none of them is paired.

The processor 5 is further configured to schedule transmissions tomobile client devices 16-19 on the selected subset of candidate downlinkfrequency resources and transmissions from the mobile client devices16-19 on the selected subset of uplink frequency resources. The selectedsubset of candidate downlink frequency resources is not based onfeedback received from the mobile client devices 16-19. The selectedsubset of candidate uplink frequency resources is not based on a channelquality measured from a reception of a transmission by the mobile clientdevices 16-19.

The processor 5 is configured to use the transceiver 3 to transmitwireless signals, specifically pilot signals, on the plurality ofcandidate downlink frequency resources. The processor 5 is configured touse the transceiver 3 to inform the plurality of static client devices11-15 of at least one time at which it will start transmitting thewireless signals on the plurality of candidate downlink frequencyresources.

In the embodiment shown in FIG. 2, the base station 1 comprises oneprocessor 5. In an alternative embodiment, the base station 1 comprisesmultiple processors. The processor 5 of the base station 1 may be ageneral-purpose processor, e.g. an Intel or an AMD processor, or anapplication-specific processor, for example. The processor 5 maycomprise multiple cores, for example. The processor 5 may run aUnix-based or Windows operating system, for example. The transceiver 3of the base station 1 may use one or more cellular communicationtechnologies such as GPRS, CDMA, UMTS, NB-IoT and/or LTE to communicatewith the client devices 11-19, for example. In the embodiment shown inFIG. 2, a receiver and a transmitter are combined in the transceiver 3of the base station 1. In an alternative embodiment, the base station 1comprises a receiver and a transmitter that are separate. The storagemeans 7 may comprise solid state memory, e.g. one or more Solid StateDisks (SSDs) made out of Flash memory, or one or more hard disks, forexample. The base station 1 may comprise other components typical for acomponent in a mobile communication network, e.g. a power supply, ortypical for a base station, e.g. an array of antennas. In the embodimentshown in FIG. 2, the base station 1 comprises one device. In analternative embodiment, the base station 1 comprise multiple devices.

In the embodiment shown in FIG. 2, the static client device 11 comprisesone processor 35. In an alternative embodiment, the static client device11 comprises multiple processors. The processor 35 may be ageneral-purpose processor, e.g. an ARM processor, or anapplication-specific processor. The processor 35 may run a Unix-basedoperating system, for example. The transceiver 33 of the static clientdevice 11 may use one or more cellular communication technologies suchas e.g. GPRS, CDMA, UMTS, NB-IoT (Narrow Band-Internet of Things) and/orLTE to communicate with the base station 1, for example. In theembodiment shown in FIG. 2, a receiver and a transmitter are combined inthe transceiver 33 of the static client device 11. In an alternativeembodiment, the static client device 11 comprises a receiver and atransmitter that are separate. The sensor 39 may comprise one or morecameras and/or one or more microphones, for example. The static clientdevice 11 may comprise other components typical for a client device,e.g. a battery.

In the embodiment shown in FIG. 2, the system for schedulingtransmissions to client devices is a base station. In an alternativeembodiment, the system may comprise a base station plus one or moreother components/functions of a mobile communication network, e.g. plusa physical or virtual node which schedules transmissions to clientdevices. The system may comprise multiple base stations distributed overmultiple sites or one base station working with multiple distributedantennas at different locations (Remote Radio Head (RRH) concept), forexample.

First embodiments of the method of scheduling transmissions to clientdevices and the method of transmitting feedback are shown in FIG. 3. Astep 51 comprises a client device transmitting pilot signals (e.g. LTESounding Reference Signals or pilot signals similar to LTE SoundingReference Signals) to a base station on a plurality of candidate uplinkfrequency resources. In the embodiments of FIGS. 3 to 12, the uplinkfrequency resources are frequency bands allocated as LTE PhysicalResource Blocks (PRBs). LTE uses Orthogonal Frequency-DivisionMultiplexing (OFDM) in which a large number of closely spaced orthogonalsub-carrier signals are used to carry data in parallel. In analternative embodiment, resources may be allocated to users in adifferent way. In the embodiments of FIGS. 3 to 12, the selected uplinkfrequency resources are used as NB-IoT carriers.

Step 51 is carried out in stage 121 shown in FIG. 5. Stage 121corresponds to time slots 101-105 in FIG. 5. Time slots 101-119 areindicated on timeslot bar 99. In time slot 101, static client device UE1transmits a pilot signal (up1) to the base station on candidate uplinkNB-IoT carrier 95, static client device UE3 transmits a pilot signal(up3) to the base station on candidate uplink NB-IoT carrier 96, andstatic client device UE2 transmits a pilot signal (up2) to the basestation on candidate uplink NB-IoT carrier 97. In time slot 102, UE2transmits a pilot signal (up2) to the base station on candidate uplinkNB-IoT carrier 95, UE1 transmits a pilot signal (up1) to the basestation on candidate uplink carrier 96, and UE3 transmits a pilot signal(up3) to the base station on candidate uplink NB-IoT carrier 98.

In time slot 103, UE3 transmits a pilot signal (up3) to the base stationon candidate uplink NB-IoT carrier 95, UE1 transmits a pilot signal(up1) to the base station on candidate uplink NB-IoT carrier 97, and UE2transmits a pilot signal (up2) to the base station on candidate uplinkNB-IoT carrier 98. In time slot 104, UE2 transmits a pilot signal (up2)to the base station on candidate uplink NB-IoT carrier 96, UE3 transmitsa pilot signal (up3) to the base station on candidate uplink NB-IoTcarrier 97, and UE1 transmits a pilot signal (up1) to the base stationon candidate uplink NB-IoT carrier 98. In the embodiment of FIG. 5 (andalso in the embodiments of FIGS. 6 and 9-12), UE1 to UE3 do not transmitsimultaneously on a single candidate uplink NB-IoT carrier. In analternative embodiment, multiple of the UEs transmit on a singlecandidate uplink NB-IoT carrier simultaneously in at least one timeslot. This may be used to reduce the length of stage 121 of FIG. 5 (andstage 125 of FIG. 6 and stage 127 of FIGS. 9-12).

A step 52 comprises the base station receiving the pilot signals fromthe client device and from further ones of the plurality of clientdevices. A step 53 comprises the base station measuring channelqualities (e.g. pilot signal level) on the plurality of candidate uplinkNB-IoT carriers from receptions of transmissions of the pilot signals.The plurality of client devices comprises one or more active clientdevices and/or one or more idle client devices. By analyzing the channelqualities, the base station can estimate if and where the ‘fade dip’ inthe uplink is. This ‘fade dip’ may be on different frequency positonbetween downlink and uplink for the frequency division duplexing (FDD)communication. While for the Time division duplexing (TDD)communication, there is symmetry between downlink and uplink.

A step 54 comprises selecting a subset of the plurality of the candidateuplink NB-IoT carriers based on the measured channel qualities. Whichcarriers have been selected may be communicated via aselected/configured downlink carrier. A step 55 comprises schedulingtransmissions to the plurality of client devices on the manuallyconfigured downlink NB-IoT carrier(s) and transmissions from theplurality of client devices on the selected subset of uplink NB-IoTcarriers. Step 55 is performed repeatedly for a certain period, e.g.hours, days, weeks, or months, after which steps 51 to 54 are repeated.Steps 51 to 54 may be performed at the initial deployment of NB-IoT, andoptionally repeated afterwards e.g. periodically in order to account forthe changes at NB-IoT client devices (e.g. deployment of new NB-IoTclient devices and/or movements of existing NB-IoT client devices).Optionally, the periodicity of this scheme may be adapted while thescheme is being performed, e.g. based on an expectation of how quicklythere might be (significant) changes at NB-IoT client devices.

The scheduled transmissions take place in time slots 106-119 shown inFIG. 5. In time slots 107-109, the base station transmits data (dd1) toUE1 on manually configured downlink NB-IoT carrier 91. In time slots111-112, the base station transmits data (dd3) to UE3 on downlinkcarrier 91. In time slots 116-117, the base station transmits data (dd2)to UE2 on downlink NB-IoT carrier 91. In time slot 109, UE2 transmitsdata (ud2) to the base station on selected uplink NB-IoT carrier 96. Intime slots 114-115, UE1 transmits data (ud1) to the base station onselected uplink NB-IoT carrier 96. In time slots 117-118, UE3 transmitsdata (ud3) to the base station on selected uplink NB-IoT carrier 96.

In the embodiment of FIG. 5 (and also in the embodiments of FIGS. 6 and9-12), transmissions to/from UEs are multiplexed in the time domain. Inan alternative embodiment, the transmissions to/from UEs are multiplexedin the frequency domain (different subcarriers are used by differentUEs), or in both time and frequency domains. In the embodiment of FIG. 5(and also in the embodiments of FIGS. 6 and 9-12), only a singledownlink NB-IoT carrier and a single uplink NB-IoT carrier are used fortransmissions to/from UEs. In an alternative embodiment, multipledownlink NB-IoT carriers and/or multiple uplink NB-IoT carriers are usedfor transmissions to/from UEs.

Second embodiments of the method of scheduling transmissions to clientdevices and the method of transmitting feedback are shown in FIG. 4. Astep 61 comprises a base station transmitting pilot signals to aplurality of client devices on a plurality of candidate downlink NB-IoTcarriers. The plurality of client devices comprises one or more activeclient devices and/or one or more idle client devices. The pilot signalscould be LTE Cell Specific Reference Signals or Narrowband ReferenceSignals (NRS) as specified for NB-IoT, for example.

NB-IoT client devices are currently only able to measure one singledownlink PRB (i.e. not multiple PRBs at the same time) due to thereception/transmission bandwidth limit of the receiver, e.g. thereceiver is simple, because the client device needs to be low cost. Theclient devices therefore listen on each of the candidate downlink NB-IoTcarriers in sequence. This procedure introduces some overhead in usingradio resource and the time spent, as well as overhead for a clientdevice in measuring and reporting. On the other hand, this proceduretypically only happens once per e.g. hour, day, week, or a month, so theoverhead is manageable. Furthermore, this procedure could be scheduledat a time when there is little traffic in the network (e.g. at night),in order to mitigate the impact.

Step 61 is carried out in stage 123 shown in FIG. 6. Stage 123corresponds to time slots 101-105 in FIG. 6. In time slots 101-105, thebase station transmits a pilot signal (dp) on candidate downlink NB-IoTcarrier 91, on candidate downlink NB-IoT carrier 92, on candidatedownlink NB-IoT carrier 93 and on candidate downlink NB-IoT carrier 94.In the embodiment of FIG. 6 (and also in the embodiments of FIGS. 9-12),the pilot signal (dp) is transmitted on all of the candidate downlinkNB-IoT carriers simultaneously. In an alternative embodiment, the pilotsignal (dp) is transmitted on the candidate downlink NB-IoT carriers insequence or according to another schedule. This may result in a moreefficient use of resources. The schedule for transmitting the pilotsignal (dp) may be standardized or communicated by the base station tothe UEs, for example.

A step 62 comprises a client device receiving these pilot signals. Astep 63 comprises the client device measuring at least one channelquality of at least one of the plurality of candidate downlink NB-IoTcarriers from at least one reception of at least one transmission by thebase station on the plurality of candidate downlink NB-IoT carriers. Astep 64 comprises transmitting feedback based on one or more of the atleast one measured channel quality to the base station on a single,manually configured uplink NB-IoT carrier.

Step 64 is carried out in stage 125 shown in FIG. 6. Stage 125corresponds to time slots 106-108 in FIG. 6. In time slot 106, UE1transmits its feedback (f1) to the base station on manually configureduplink NB-IoT carrier 95. In time slot 107, UE2 transmits its feedback(f2) to the base station on uplink NB-IoT carrier 95. In time slot 108,UE3 transmits its feedback (f3) to the base station on uplink NB-IoTcarrier 95. In the embodiment of FIG. 4, illustrated in FIG. 6, thefeedback identifies which one or more of candidate downlink NB-IoTcarriers 91-94 is or are preferred by the client device. The period inwhich stages 123 and 125 take place may be pre-configured in the basestation and in the client devices or communicated by the base station tothe client devices, for example. In the embodiment of FIG. 6, thefeedback transmitted by the UEs is multiplexed in the time domain. In analternative embodiment, the feedback transmitted by the UEs ismultiplexed in the frequency domain (different subcarriers are used bydifferent UEs), or in both time and frequency domains.

A step 65 comprises the base station receiving this feedback from theclient device and receiving further feedback from the further ones ofthe plurality of client devices. A step 66 comprises selecting a subsetof the plurality of candidate downlink NB-IoT carriers based on thereceived feedback. Step 55 comprises scheduling transmissions to theplurality of client devices on the selected subset of candidate downlinkNB-IoT carriers and transmissions from the plurality of client deviceson the manually configured uplink NB-IoT carrier(s).

The scheduled transmissions take place in time slots 109-119 shown inFIG. 6. In time slots 110-112, the base station transmits data (dd1) toUE1 on selected downlink NB-IoT carrier 92. In time slots 114-115, thebase station transmits data (dd3) to UE3 on selected downlink NB-IoTcarrier 92. In time slots 118-119, the base station transmits data (dd2)to UE2 on selected downlink NB-IoT carrier 92. In time slot 111, UE2transmits data (ud2) to the base station on manually configured uplinkNB-IoT carrier 95. In time slots 114-115, UE1 transmits data (ud1) tothe base station on manually configured uplink NB-IoT carrier 95. Intime slots 118-119, UE3 transmits data (ud3) to the base station onmanually configured uplink NB-IoT carrier 95.

Third embodiments of the method of scheduling transmissions to clientdevices and the method of transmitting feedback are shown in FIG. 7.Steps 61, 62 and 63 are the same as in FIG. 4. However, step 64 of FIG.4 has been replaced with a step 71 in FIG. 7. Step 71 comprisestransmitting feedback based on one or more of the at least one measuredchannel quality of at least one of the plurality of candidate downlinkNB-IoT carriers to the base station on a plurality of candidate uplinkNB-IoT carriers.

Step 71 is carried out in stage 127 shown in FIG. 9. Stage 127corresponds to time slots 106-109 in FIG. 9. In time slot 106, UE1transmits its feedback relating to candidate downlink carrier 91 (f1a)to the base station on candidate uplink NB-IoT carrier 95, UE3 transmitsits feedback relating to candidate downlink carrier 92 (f3b) to the basestation on candidate uplink NB-IoT carrier 96 and UE2 transmits itsfeedback relating to candidate downlink NB-IoT carrier 93 (f2c) to thebase station on candidate uplink NB-IoT carrier 97. In time slot 107,UE2 transmits its feedback relating to candidate downlink NB-IoT carrier91 (f2a) to the base station on candidate uplink NB-IoT carrier 95, UE1transmits its feedback relating to candidate downlink NB-IoT carrier 92(f1b) to the base station on candidate uplink NB-IoT carrier 96 and UE3transmits its feedback relating to candidate downlink NB-IoT carrier 94(f3d) to the base station on candidate uplink NB-IoT carrier 98.

In time slot 108, UE3 transmits its feedback relating to candidatedownlink carrier 91 (f3a) to the base station on candidate uplink NB-IoTcarrier 95, UE1 transmits its feedback relating to candidate downlinkNB-IoT carrier 93 (f1c) to the base station on candidate uplink NB-IoTcarrier 97 and UE2 transmits its feedback relating to candidate downlinkNB-IoT carrier 94 (f2d) to the base station on candidate uplink NB-IoTcarrier 98. In time slot 109, UE2 transmits its feedback relating tocandidate downlink NB-IoT carrier 92 (f2b) to the base station oncandidate uplink NB-IoT carrier 96, UE3 transmits its feedback relatingto candidate downlink NB-IoT carrier 93 (f3c) to the base station oncandidate uplink NB-IoT carrier 97 and UE1 transmits its feedbackrelating to candidate downlink NB-IoT carrier 94 (f1d) to the basestation on candidate uplink NB-IoT carrier 98. In the embodiment of FIG.7, illustrated in FIG. 9, the feedback comprises the Received SignalReceived Power (RSRP) of a single downlink carrier. In an alternativeembodiment, the feedback additionally or alternatively comprises otherperformance metrics like RSRQ, CQI, SNR, SINR.

A step 72 comprises the base station receiving the feedback from theclient devices on the plurality of candidate uplink NB-IoT carriers. Astep 73 comprises the base station measuring channel qualities on theplurality of candidate uplink NB-IoT carriers from receptions of thefeedback from the plurality of client devices. A step 74 comprisesselecting a subset of the plurality of candidate downlink NB-IoTcarriers and a subset of the plurality of candidate uplink NB-IoTcarriers based on the received feedback and the measured channelqualities.

Step 55 comprises scheduling transmissions to the plurality of clientdevices on the selected subset of candidate downlink NB-IoT carriers andtransmissions from the plurality of client devices on the selectedsubset of candidate uplink NB-IoT carriers. In the embodiment of FIG. 7,the uplink NB-IoT carriers and the downlink NB-IoT carriers are paired,i.e. an uplink NB-IoT carrier has a pre-defined relative frequencyposition to the downlink NB-IoT carrier (where the base station hastransmitted the pilot signal). In this case, the base station implicitlyknows for which downlink carrier the feedback received in step 72 is.

The scheduled transmissions take place in time slots 110-119 shown inFIG. 9. In time slots 111-113, the base station transmits data (dd1) toUE1 on selected downlink NB-IoT carrier 92. In time slots 115-116, thebase station transmits data (dd3) to UE3 on selected downlink NB-IoTcarrier 92. In time slots 118-119, the base station transmits data (dd2)to UE2 on selected downlink NB-IoT carrier 92. In time slot 111, UE2transmits data (ud2) to the base station on selected uplink NB-IoTcarrier 96. In time slots 114-115, UE1 transmits data (ud1) to the basestation on selected uplink NB-IoT carrier 96. In time slots 118-119, UE3transmits data (ud3) to the base station on selected uplink NB-IoTcarrier 96.

Fourth embodiments of the method of scheduling transmissions to clientdevices and the method of transmitting feedback are shown in FIG. 8. Inthese fourth embodiments, the uplink NB-IoT carriers and the downlinkNB-IoT carriers are not paired, i.e. there is no uplink NB-IoT carrierthat has a one-to-one relation with the downlink carrier where the basestation has transmitted the pilot signal. Steps 61 to 63, steps 71 to 73and step 55 are the same as in FIG. 7. Step 74 of FIG. 7 has beenreplaced with step 54 of FIG. 3 and step 66 of FIG. 4. Since the uplinkNB-IoT carriers and the downlink NB-IoT carriers are not paired, theyare selected separately, which may result in better performance. This isillustrated in FIG. 10.

The difference between FIGS. 9 and 10 is that in FIG. 10, candidateuplink NB-IoT carrier 95 has been selected instead of candidate uplinkNB-IoT carrier 96. In FIG. 9, downlink NB-IoT carrier 91 is paired withuplink NB-IoT carrier 95, downlink carrier 92 is paired with uplinkNB-IoT carrier 96, downlink NB-IoT carrier 93 is paired with uplinkNB-IoT carrier 97, and downlink NB-IoT carrier 94 is paired with uplinkNB-IoT carrier 98. Thus, the selected downlink NB-IoT carrier 92 and theselected uplink NB-IoT carrier 96 of FIG. 9 are paired and the selecteddownlink NB-IoT carrier 92 and the selected uplink NB-IoT carrier 95 ofFIGS. 10-12 are not paired.

In time slot 111 of FIG. 10, UE2 transmits data (ud2) to the basestation on selected uplink NB-IoT carrier 95. In time slots 114-115 ofFIG. 10, UE1 transmits data (ud1) to the base station on selected uplinkNB-IoT carrier 95. In time slots 118-119 of FIG. 10, UE3 transmits data(ud3) to the base station on selected uplink NB-IoT carrier 95. In FIG.10, the feedback transmitted by the client devices in stage 127 is thesame as in FIG. 9. Although the selected downlink NB-IoT carrier 92 andthe selected uplink NB-IoT carrier 95 are not paired, the pairingbetween downlink NB-IoT carriers and uplink NB-IoT carriers is used instage 127 in FIG. 10.

In FIGS. 11-12, the pairing between downlink NB-IoT carriers and uplinkNB-IoT carriers is not used in stage 127. In FIG. 11, the feedbacktransmitted on an uplink NB-IoT carrier does not relate to a paireddownlink NB-IoT carrier, but identifies to which downlink NB-IoT carrierit does relate. Like in FIGS. 9 and 10, the feedback comprises theReceived Signal Received Power (RSRP) of a single downlink NB-IoTcarrier. In an alternative embodiment, the feedback additionally oralternatively comprises other performance metrics like RSRQ, CQI, SNR,SINR.

In time slot 106 of FIG. 11, UE1 transmits its feedback relating tocandidate downlink NB-IoT carrier 91 (f1a) to the base station oncandidate uplink NB-IoT carrier 95, UE3 transmits its feedback relatingto candidate downlink NB-IoT carrier 93 (f3c) to the base station oncandidate uplink NB-IoT carrier 96 and UE2 transmits its feedbackrelating to candidate downlink NB-IoT carrier 94 (f2d) to the basestation on candidate uplink NB-IoT carrier 97. In time slot 107 of FIG.11, UE2 transmits its feedback relating to candidate downlink NB-IoTcarrier 92 (f2b) to the base station on candidate uplink NB-IoT carrier95, UE1 transmits its feedback relating to candidate downlink NB-IoTcarrier 92 (f1b) to the base station on candidate uplink NB-IoT carrier96 and UE3 transmits its feedback relating to candidate downlink NB-IoTcarrier 91 (f3a) to the base station on candidate uplink NB-IoT carrier98.

In time slot 108 of FIG. 11, UE3 transmits its feedback relating tocandidate downlink NB-IoT carrier 94 (f3d) to the base station oncandidate uplink NB-IoT carrier 95, UE1 transmits its feedback relatingto candidate downlink NB-IoT carrier 93 (f1c) to the base station oncandidate uplink NB-IoT carrier 97 and UE2 transmits its feedbackrelating to candidate downlink NB-IoT carrier 91 (f2a) to the basestation on candidate uplink NB-IoT carrier 98. In time slot 109 of FIG.11, UE2 transmits its feedback relating to candidate downlink NB-IoTcarrier 93 (f2c) to the base station on candidate uplink NB-IoT carrier96, UE3 transmits its feedback relating to candidate downlink NB-IoTcarrier 92 (f3b) to the base station on candidate uplink NB-IoT carrier97 and UE1 transmits its feedback relating to candidate downlink NB-IoTcarrier 94 (f1d) to the base station on candidate uplink NB-IoT carrier98.

In FIG. 12, the feedback transmitted on a candidate uplink NB-IoTcarrier identifies which one or more of candidate downlink NB-IoTcarriers 91-94 is or are preferred by the client device, like in FIG. 6.However, since feedback should be transmitted on multiple candidateuplink NB-IoT carriers, a client device transmits the same feedback onall the candidate uplink NB-IoT carriers 95-98. UE1 transmits itsfeedback on candidate uplink NB-IoT carrier 95 in time slot 106, oncandidate uplink NB-IoT carrier 96 in time slot 107, on candidate uplinkNB-IoT carrier 97 in time slot 108 and on candidate uplink NB-IoTcarrier 98 in time slot 109.

UE2 transmits its feedback on candidate uplink NB-IoT carrier 95 in timeslot 107, on candidate uplink NB-IoT carrier 96 in time slot 109, oncandidate uplink NB-IoT carrier 97 in time slot 106 and on candidateuplink NB-IoT carrier 98 in time slot 108. UE3 transmits its feedback oncandidate uplink NB-IoT carrier 95 in time slot 108, on candidate uplinkNB-IoT carrier 96 in time slot 106, on candidate uplink NB-IoT carrier97 in time slot 109 and on candidate uplink NB-IoT carrier 98 in timeslot 107.

FIGS. 5-6 and 9-12 show the use of Frequency Division Multiplexing(FDD). In an alternative embodiment, Time Division Multiplexing (TDD) isused. In this alternative embodiment, the same frequency resources areused for both uplink and downlink and downlink and uplink frequencyresources thus do not need to be paired.

Step 54 of FIGS. 3 and 8, step 66 of FIGS. 4 and 8, and step 74 of FIG.7 at least comprise selecting one or more NB-IoT anchor carriers and mayoptionally comprise selecting one or more NB-IoT non-anchor carriers.The base station/network may perform this selection, for example, byfirst determining for each candidate carrier how many of the clientdevices can be served on this candidate carrier (e.g. by determiningwhether a determined RSRP in the downlink or a measured signal strengthin the uplink exceeds a certain threshold).

For example, a first candidate downlink carrier may be able to serve 85%of the client devices, a second candidate downlink carrier may be ableto serve 82% of the client devices, a third candidate downlink carriermay be able to serve 78% of the client devices, and a fourth candidatedownlink carrier may be able to serve 74% of the client devices. A firstcandidate uplink carrier may be able to serve 83% of the client devices,a second candidate uplink carrier may be able to serve 80% of the clientdevices, a third candidate uplink carrier may be able to serve 79% ofthe client devices, and a fourth candidate uplink carrier may be able toserve 76% of the client devices.

A single downlink carrier and/or a single uplink carrier may be selectedor multiple downlink carriers and/or multiple uplink carriers may beselected. In the former case, the selected downlink carrier may be thefirst candidate downlink carrier (serving 85% of the client devices)and/or the selected uplink carrier may be the first candidate uplinkcarrier (serving 83% of the client devices), for example.

In the latter case, the base station/network may use, for example, oneof the following criteria for selecting multiple carriers based on thedetermined information:

-   A. The base station/network selects the M downlink carriers (of    which at least one is an anchor carrier) and/or uplink carriers (of    which at least one is an anchor carrier) which together serve all    the NB-IoT client devices, or as many of the NB-IoT client devices    as possible. For example, the first and the fourth candidate    downlink carriers are selected, because together they serve 95% of    the client devices, while the first and the second candidate    downlink carriers together serve, 90% of the client devices, and/or    the first and the third candidate uplink carriers are selected,    because together they serve 90% of the client devices, while the    first and the second candidate uplink carriers together serve, 85%    of the client devices.-   B. The base station/network selects the M downlink carriers (of    which at least one is an anchor carrier) and/or uplink carriers (of    which at least one is an anchor carrier) which are ranked the    highest. For example, the first candidate downlink carrier and the    second candidate downlink carrier are selected and/or the first    candidate uplink carrier and the second candidate uplink carrier are    selected, because they are ranked highest according to the    percentage of served client devices.

When determining how many client devices can be served with a candidatedownlink carrier, it may be taken into account whether these clientdevices can be served by the statically configured uplink carriers orcandidate uplink carriers. When determining how many client devices canbe served with a candidate uplink carrier, it may be taken into accountwhether these client devices can be served by the statically configureddownlink carriers or candidate downlink carriers. For example, the firstcandidate uplink carrier and the first candidate downlink carrier mighttogether be able to serve 75% of the client devices in both uplink anddownlink, while the second candidate downlink carrier and the secondcandidate uplink carrier might together be able to serve 80% of theclient devices in both uplink and downlink. In this case, the lattercombination may be preferred.

A combined quality of a paired downlink frequency resource and uplinkfrequency resource may be determined in one of the following ways, forexample:

-   1. Determining the sum of the number of served client devices in the    downlink and the number of served client devices in the uplink-   2. Determining the number of served client devices in the downlink,    with the condition that the number of client devices served by the    paired uplink carrier is no lower than a pre-defined threshold-   3. Determining the number of served client devices in the uplink,    with the condition that the number of client devices served by the    paired downlink carrier is no lower than a pre-defined threshold

The measurements performed in step 53 of FIG. 3 and step 73 of FIGS. 7and 8 and the feedback received in steps 65 of FIG. 4 and step 72 ofFIGS. 7 and 8 may be used in step 55 to determine which time-frequencyresources to allocate to a client device if multiple downlink NB-IoTcarriers and/or multiple downlink NB-IoT have been selected/configured.

In the telecommunications system 200 of FIG. 13, three generations ofnetworks are schematically depicted together for purposes of brevity. Amore detailed description of the architecture and overview can be foundin 3GPP Technical Specification TS 23.002 ‘Network Architecture’ whichis included in the present application by reference in its entirety.Other types of cellular telecommunication system can alternatively oradditionally be used, e.g. a 5G cellular telecommunication system.

The lower branch of FIG. 13 represents a GSM/GPRS or UMTS network.

For a GSM/GPRS network, a radio access network (RAN) system 220comprises a plurality of nodes, including base stations (combination ofa BSC and a BTS), not shown individually in FIG. 13. The core networksystem comprises a Gateway GPRS Support Node 222 (GGSN), a Serving GPRSSupport Node 221 (SGSN, for GPRS) or Mobile Switching Centre (MSC, forGSM, not shown in FIG. 6) and a Home Location Register 223 (HLR). TheHLR 223 contains subscription information for user devices 201, e.g.mobile stations MS.

For a UMTS radio access network (UTRAN), the radio access network system220 also comprises a Radio Network Controller (RNC) connected to aplurality of base stations (NodeBs), also not shown individually in FIG.13. In the core network system, the GGSN 222 and the SGSN 221/MSC areconnected to the HLR 223 that contains subscription information of theuser devices 201, e.g. user equipment UE.

The upper branch of the telecommunications system in FIG. 13 representsa next generation network, commonly indicated as Long Term Evolution(LTE) system or Evolved Packet System (EPS).

The radio access network system 210 (E-UTRAN), comprises base stations(evolved NodeBs, eNodeBs or eNBs), not shown individually in FIG. 13,providing cellular wireless access for a user device 201, e.g. userequipment UE. The core network system comprises a PDN Gateway (P-GW) 214and a Serving Gateway 212 (S-GW). The E-UTRAN 210 of the EPS isconnected to the S-GW 212 via a packet network. The S-GW 212 isconnected to a Home Subscriber Server HSS 213 and a Mobility ManagementEntity MME 211 for signalling purposes. The HSS 213 includes asubscription profile repository SPR for user devices 201.

For GPRS, UMTS and LTE systems, the core network system is generallyconnected to a further packet network 202, e.g. the Internet.

Further information of the general architecture of an EPS network can befound in 3GPP Technical Specification TS 23.401 ‘GPRS enhancements forEvolved Universal Terrestrial Radio Access Network (E-UTRAN) access’.

FIG. 14 depicts a block diagram illustrating an exemplary dataprocessing system that may perform the methods as described withreference to FIGS. 3-4 and 7-8.

As shown in FIG. 14, the data processing system 300 may include at leastone processor 302 coupled to memory elements 304 through a system bus306. As such, the data processing system may store program code withinmemory elements 304. Further, the processor 302 may execute the programcode accessed from the memory elements 304 via a system bus 306. In oneaspect, the data processing system may be implemented as a computer thatis suitable for storing and/or executing program code. It should beappreciated, however, that the data processing system 300 may beimplemented in the form of any system including a processor and a memorythat is capable of performing the functions described within thisspecification.

The memory elements 304 may include one or more physical memory devicessuch as, for example, local memory 308 and one or more bulk storagedevices 310. The local memory may refer to random access memory or othernon-persistent memory device(s) generally used during actual executionof the program code. A bulk storage device may be implemented as a harddrive or other persistent data storage device. The processing system 300may also include one or more cache memories (not shown) that providetemporary storage of at least some program code in order to reduce thenumber of times program code must be retrieved from the bulk storagedevice 310 during execution.

Input/output (I/O) devices depicted as an input device 312 and an outputdevice 314 optionally can be coupled to the data processing system.Examples of input devices may include, but are not limited to, akeyboard, a pointing device such as a mouse, or the like. Examples ofoutput devices may include, but are not limited to, a monitor or adisplay, speakers, or the like. Input and/or output devices may becoupled to the data processing system either directly or throughintervening I/O controllers.

In an embodiment, the input and the output devices may be implemented asa combined input/output device (illustrated in FIG. 14 with a dashedline surrounding the input device 312 and the output device 314). Anexample of such a combined device is a touch sensitive display, alsosometimes referred to as a “touch screen display” or simply “touchscreen”. In such an embodiment, input to the device may be provided by amovement of a physical object, such as e.g. a stylus or a finger of auser, on or near the touch screen display.

A network adapter 316 may also be coupled to the data processing systemto enable it to become coupled to other systems, computer systems,remote network devices, and/or remote storage devices throughintervening private or public networks. The network adapter may comprisea data receiver for receiving data that is transmitted by said systems,devices and/or networks to the data processing system 300, and a datatransmitter for transmitting data from the data processing system 300 tosaid systems, devices and/or networks. Modems, cable modems, andEthernet cards are examples of different types of network adapter thatmay be used with the data processing system 300.

As pictured in FIG. 14, the memory elements 304 may store an application318. In various embodiments, the application 318 may be stored in thelocal memory 308, the one or more bulk storage devices 310, or separatefrom the local memory and the bulk storage devices. It should beappreciated that the data processing system 300 may further execute anoperating system (not shown in FIG. 14) that can facilitate execution ofthe application 318. The application 318, being implemented in the formof executable program code, can be executed by the data processingsystem 300, e.g., by the processor 302. Responsive to executing theapplication, the data processing system 300 may be configured to performone or more operations or method steps described herein.

Various embodiments of the invention may be implemented as a programproduct for use with a computer system, where the program(s) of theprogram product define functions of the embodiments (including themethods described herein). In one embodiment, the program(s) can becontained on a variety of non-transitory computer-readable storagemedia, where, as used herein, the expression “non-transitory computerreadable storage media” comprises all computer-readable media, with thesole exception being a transitory, propagating signal. In anotherembodiment, the program(s) can be contained on a variety of transitorycomputer-readable storage media. Illustrative computer-readable storagemedia include, but are not limited to: (i) non-writable storage media(e.g., read-only memory devices within a computer such as CD-ROM disksreadable by a CD-ROM drive, ROM chips or any type of solid-statenon-volatile semiconductor memory) on which information is permanentlystored; and (ii) writable storage media (e.g., flash memory, floppydisks within a diskette drive or hard-disk drive or any type ofsolid-state random-access semiconductor memory) on which alterableinformation is stored. The computer program may be run on the processor302 described herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of embodiments of the present invention has been presentedfor purposes of illustration, but is not intended to be exhaustive orlimited to the implementations in the form disclosed. Many modificationsand variations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the present invention.The embodiments were chosen and described in order to best explain theprinciples and some practical applications of the present invention, andto enable others of ordinary skill in the art to understand the presentinvention for various embodiments with various modifications as aresuited to the particular use contemplated.

The invention claimed is:
 1. A system for scheduling transmissions toclient devices, comprising: at least one receiver; and at least oneprocessor configured to: use said at least one receiver to receivefeedback about a plurality of candidate downlink frequency resourcesfrom a plurality of client devices and/or measure channel qualities of aplurality of candidate uplink frequency resources from receptions oftransmissions by said plurality of client devices, select a subset ofsaid plurality of candidate downlink frequency resources and/or a subsetof said plurality of candidate uplink frequency resources based on saidreceived feedback and/or said measured channel qualities, and scheduletransmissions to said plurality of client devices on said selectedsubset of candidate downlink frequency resources and/or transmissionsfrom said plurality of client devices on said selected subset of uplinkfrequency resources.
 2. A system as claimed in claim 1, wherein said atleast one processor is configured to use said at least one receiver toreceive said feedback about said plurality of candidate downlinkfrequency resources on said plurality of candidate uplink frequencyresources and measure said channel quality of said plurality ofcandidate uplink frequency resources from receptions of said feedback onsaid plurality of candidate uplink frequency resources.
 3. A system asclaimed in claim 1, wherein at least one of said plurality of candidatedownlink frequency resources is paired with at least one of saidplurality of candidate uplink frequency resources and said at least oneprocessor is configured to use said at least one receiver to receivesaid feedback about said at least one candidate downlink frequencyresource on the at least one candidate uplink frequency resource pairedwith said at least one candidate downlink frequency resource.
 4. Asystem as claimed in claim 1, wherein said feedback comprises anidentification of one or more candidate downlink frequency resources towhich said feedback relates.
 5. A system as claimed in claim 1, whereinat least one of said plurality of candidate downlink frequency resourcesis paired with at least one of said plurality of candidate uplinkfrequency resources and said at least one processor is configured todetermine at least one combined quality for at least one pair ofcandidate downlink and uplink frequency resources and select a subset ofsaid plurality of candidate downlink frequency resources and a subset ofsaid plurality of candidate uplink frequency resources based on said atleast one combined quality.
 6. A system-as claimed in claim 1, whereinsaid at least one processor is further configured to scheduletransmissions to a mobile client device on said selected subset ofcandidate downlink frequency resources and/or transmissions from saidmobile client device on said selected subset of uplink frequencyresources, said selected subset of candidate downlink frequencyresources not being based on feedback received from said mobile clientdevice and/or said selected subset of candidate uplink frequencyresources not being based on a channel quality measured from a receptionof a transmission by said mobile client device.
 7. A system as claimedin claim 1, wherein said system further comprises at least onetransmitter and said at least one processor is configured to use said atleast one transmitter to transmit wireless signals on said plurality ofcandidate downlink frequency resources.
 8. A system as claimed in claim7, wherein said wireless signals transmitted by said at least oneprocessor using said at least one transmitter on said plurality ofcandidate downlink frequency resources are pilot signals.
 9. A system asclaimed in claim 7, wherein said at least one processor is configured touse said at least one transmitter to inform said plurality of clientdevices of at least one time at which it will start transmitting saidwireless signals on said plurality of candidate downlink frequencyresources.
 10. A client device for transmitting feedback, said clientdevice comprising: at least one receiver; at least one transmitter; andat least one processor configured to: use said at least one receiver tomeasure at least one channel quality of at least one candidate downlinkfrequency resource from at least one reception of at least onetransmission by a transmitting system on said at least one candidatedownlink frequency resource, and use said at least one transmitter totransmit feedback based on one or more of said at least one measuredchannel quality to said transmitting system on a plurality of candidateuplink frequency resources.
 11. A method of scheduling transmissions toclient devices, comprising: receiving feedback, about a plurality ofcandidate downlink frequency resources from a plurality of clientdevices and/or measuring channel qualities of a plurality of candidateuplink frequency resources from receptions of transmissions by saidplurality of client devices; selecting a subset of said plurality ofcandidate downlink frequency resources and/or a subset of said pluralityof said candidate uplink frequency resources based on said receivedfeedback and/or said measured channel qualities; and schedulingtransmissions to said plurality of client devices on said selectedsubset of candidate downlink frequency resources and/or transmissionsfrom said plurality of client devices on said selected subset of uplinkfrequency resources.
 12. A method of transmitting feedback, comprising:measuring at least one channel quality of at least one candidatedownlink frequency resource from at least one reception of at least onetransmission by a transmitting system on said at least one candidatedownlink frequency resource; and transmitting feedback based on one ormore of said at least one measured channel quality to said transmittingsystem on a plurality of candidate uplink frequency resources.
 13. Anon-transitory computer-readable medium comprising a computer program,the computer program comprising instructions for causing a processorsystem to perform the method of claim
 11. 14. A non-transitorycomputer-readable medium comprising a computer program, the computerprogram comprising instructions for causing a processor system toperform the method of claim 12.